Factors shaping European rabbit abundance

Breaking barriers: Iberian Lynx Lynx pardinus Temminck, 1827 (Mammalia: Carnivora: Felidae) colonizing Olive groves

In recent years, the Andújar-Cardeña Iberian Lynx Lynx pardinus population has grown both in number and in occupied surface area.  This feline has spread into areas surrounding existing population nuclei and occupied new habitats including human-dominated areas and tree crops.  Here we describe this colonization process and the evolution of the Iberian Lynx populations in the Olive Olea europaea groves that surround typical Lynx scrub habitats in Andújar-Cardeña.  Our findings were obtained through radio-tracking, camera trapping and European Rabbit Oryctolagus cuniculus monitoring.  Two colonized areas—Zocueca and Marmolejo-Montoro—were identified in which Olive cultivation is predominant.  Since 2011, a total of 45 and 50 different individuals have been detected in Zocueca and Marmolejo-Montoro, respectively.  At present, 19 individuals are known to live in Zocueca and 29 in Marmolejo-Montoro.  The main cause of mortality is road-kills.  Our results suggest that the Iberian Lynx is capable of colonizing human-modified areas such as agricultural land provided that they can support high-density Rabbit populations and the causes of non-natural mortality are minimized.

Iberian Lynx Lynx pardinus Temminck, 1827 (Mammalia: Carnivora: Felidae) in central Spain: trophic niche of an isolated population

Understanding predator-prey relationships is fundamental to develop effective conservation plans.  Between 2015 and 2018, we combed 21 transects, each 7km long, searching for Iberian Lynx Lynx pardinus scat within the province of Madrid in central Spain.  In order to minimise inherent subjectivity of visual identification as much as possible, we performed a double specific nested polymerase chain reaction (PCR) followed by a primer extension assay addressed to two Iberian Lynx diagnostic single nucleotide polymorphisms.  Forty-six scat samples were positively identified as belonging to Iberian Lynx through genetic analysis.  From these, we extracted remains of consumed prey, which we determined to the lowest possible taxonomic level, mainly through hair identification.  Identified prey was divided into four types: lagomorphs, small mammals, birds, and ungulates.  The species’ diet composition was described based on the frequency of occurrence (FO) of each prey and niche breadth, and also compared with prior knowledge of the species using four prior studies as a comparative reference through the calculation of the niche overlap value.  The FO of lagomorphs (39%) was the lowest, while the FO of small mammals (54%) was the highest recorded to date.  The niche breath (0.36) was higher than recorded in prior studies, but still showing the specialist character of the Iberian Lynx.  Niche overlap was low (C = 0.49), showing differences in trophic niche between the population in our study area and the one studied in southern Spain.  This indicates that the Iberian Lynx is adept at switching its main prey, an ability that has previously been firmly rejected.  It is, however, capable of adapting to alternative prey more often than recorded to date, which could be a behavioural response to the patchy distribution of European Rabbit Oryctolagus cuniculus in the study area.

Planning the peninsula-wide recovery of the Iberian lynx: identification of favourable habitat areas

The creation of new populations through reintroductions in their former range is still necessary for the long-term conservation of the Iberian lynx (Lynx pardinus). A large-scale assessment of habitat suitability is a necessary prerequisite for evaluating the possibility of carrying out lynx reintroductions. We modelled habitat suitability for the Iberian lynx in the Iberian Peninsula using MaxEnt. Lynx presence data for 2010–2013 from Andujar-Cardeña and Doñana populations were used. Habitat variables were quantified using the CORINE Land Cover. This habitat suitability model predicted an environmentally suitable area of 87,747 km2, which represents 14.08% of the whole Iberian Peninsula. Of the total suitable habitat identified, 45% is located in a large continuous area in the south-western quadrant coinciding with the historical range of the species in the mid-20th century. However, there are also relevant patches mainly in the north-eastern quadrant. About 55% of the potential area suitable for the lynx falls outside protected areas. If Iberian lynx populations are to attain levels that will facilitate their long-term survival, it will be necessary to consider potential habitat for the species throughout the whole of the Iberian Peninsula.

Climate and landscape changes as driving forces for future range shift in southern populations of the European badger

Human-Induced Rapid Environmental Change (HIREC), particularly climate change and habitat conversion, affects species distributions worldwide. Here, we aimed to (i) assess the factors that determine range patterns of European badger (Meles meles) at the southwestern edge of their distribution and (ii) forecast the possible impacts of future climate and landcover changes on those patterns. We surveyed 272 cells of 5 × 5 km, to assess badger presence and confirmed its occurrence in 95 cells (35%). Our models estimate that badger’s presence is promoted by the occurrence of herbaceous fields and shrublands (5%–10%), and low proportions of Eucalyptus plantations (<~15%). Regions with >50% of podzols and eruptive rocks, higher sheep/goat density (>4 ind/km²), an absence of cattle, intermediate precipitation regimes (800–1000 mm/year) and mild mean temperatures (15–16 °C) are also more likely to host badgers. We predict a decrease in favourability of southern areas for hosting badgers under forecasted climate and landcover change scenarios, which may lead to a northwards retraction of the species southern distribution limit, but the overall landscape favourability is predicted to slightly increase. The forecasted retraction may affect community functional integrity, as its role in southern ecological networks will be vacant.

Disease-mediated bottom-up regulation: An emergent virus affects a keystone prey, and alters the dynamics of trophic webs

Emergent diseases may alter the structure and functioning of ecosystems by creating new biotic interactions and modifying existing ones, producing cascading processes along trophic webs. Recently, a new variant of the rabbit haemorrhagic disease virus (RHDV2 or RHDVb) arguably caused widespread declines in a keystone prey in Mediterranean ecosystems - the European rabbit (Oryctolagus cuniculus). We quantitatively assess the impact of RHDV2 on natural rabbit populations and in two endangered apex predator populations: the Iberian lynx (Lynx pardinus) and the Spanish Imperial eagle (Aquila adalberti). We found 60–70% declines in rabbit populations, followed by decreases of 65.7% in Iberian lynx and 45.5% in Spanish Imperial eagle fecundities. A revision of the web of trophic interactions among rabbits and their dependent predators suggests that RHDV2 acts as a keystone species, and may steer Mediterranean ecosystems to management-dependent alternative states, dominated by simplified mesopredator communities. This model system stresses the importance of diseases as functional players in the dynamics of trophic webs.

Importance of latrine communication in European rabbits shifts along a rural-to-urban gradient

Background

Information transfer in mammalian communication networks is often based on the deposition of excreta in latrines. Depending on the intended receiver(s), latrines are either formed at territorial boundaries (between-group communication) or in core areas of home ranges (within-group communication). The relative importance of both types of marking behavior should depend, amongst other factors, on population densities and social group sizes, which tend to differ between urban and rural wildlife populations. Our study is the first to assess (direct and indirect) anthropogenic influences on mammalian latrine-based communication networks along a rural-to-urban gradient in European rabbits (Oryctolagus cuniculus) living in urban, suburban and rural areas in and around Frankfurt am Main (Germany).

Results

The proportion of latrines located in close proximity to the burrow was higher at rural study sites compared to urban and suburban ones. At rural sites, we found the largest latrines and highest latrine densities close to the burrow, suggesting that core marking prevailed. By contrast, latrine dimensions and densities increased with increasing distance from the burrow in urban and suburban populations, suggesting a higher importance of peripheral marking.

Conclusions

Increased population densities, but smaller social group sizes in urban rabbit populations may lead to an increased importance of between-group communication and thus, favor peripheral over core marking. Our study provides novel insights into the manifold ways by which man-made habitat alterations along a rural-to-urban gradient directly and indirectly affect wildlife populations, including latrine-based communication networks.

Use of different areas of pen by growing rabbits depending on the elevated platforms' floor-type

The addition of platforms to rabbit cages increases their accessible area and provides rabbits greater freedom and mobility. Different types of platforms enable rabbits to situate themselves where they are most comfortable. The objective of this experiment was to analyse preference of growing rabbits between different areas of the pen depending on the elevated platforms' floor-type. Pens with a basic area of 0.84 m2 were equipped with platforms of 0.42 m2. Three types of flooring of the elevated platforms were used as treatments: deep-litter floor and an open wire-net floor (Experiment 1), and a deep-litter floor and a wire-net floor with a manure tray beneath it (Experiment 2). Growing rabbits (n = 168; 42 per treatment) between the ages of 5 and 11 weeks were studied, based on 24 h video recordings from infra-red cameras (one recording per week) applying scan sampling method with a frequency of 30 min. When the platform was deep-litter, significantly (P < 0.001) more rabbits used the area under the platform (53.7% and 54.3% in Experiments 1 and 2, respectively) than stayed on the platform (16.7% and 7.6%). In treatments of wire-net platform with and without tray beneath the platform also significantly (P < 0.001) more rabbits stayed under the platform (43.7% and 34.7%, respectively) than on the platform (19.5% and 29.9%, respectively). The differences from the expected 33.3% staying on the platform or under the platform were significant at least at the level of P < 0.05. The results show that the wire-net platform with the manure tray provides the optimal environment as it leads to the rabbits spreading themselves more evenly in the pen (i.e. the platform expands available floor area) without the risk of soiling from above, and without adverse effects on heat dissipation, and with the possibility of seeking cover when desired.

The usefulness of field data and hunting statistics in the assessment of wild rabbit (Oryctolagus cuniculus) conservation status in Portugal

Context. The wild rabbit (Oryctolagus cuniculus) is a keystone species from the Iberian Peninsula that has suffered a strong decline in Spain during the past decades. Data on historical and current population trends in Portugal are virtually non-existent. Aims. To investigate changes in rabbit abundance at the national level so as to inform conservation status assessments, and to evaluate the usefulness of hunting bags as a rabbit abundance index. Methods. Field surveys based on latrine counts in linear transects were performed in two periods (1995 and 2002) to assess variation in population abundance. Hunting bags were also analysed for the same period to verify whether these data showed the same trends. General trends of rabbit abundance were estimated using TRIM software. Key results. Field data revealed that most of the sampling units across Portugal have low abundances, despite the observation of local high-density spots. A population reduction of 27% was estimated. Although some fluctuations were observed in hunting bags, global results obtained from these data suggest a slightly increasing trend in rabbit abundance. Conclusions. A discrepancy between field data and hunting statistics was observed. Because hunting bags may be influenced by sporadic management operations undertaken by hunters and the lack of systematic procedures in data collection, we believe that hunting statistics are not representative of real changes in rabbit populations. Thus, observed reduction in rabbit abundance estimated by field data, combined with the high initial morbidity due to rabbit haemorrhagic disease (RHD) after 1988 and the potential for continuing decline in population trends because of other factors, led to an inference of a reduction of >30% in rabbit abundance in Portugal during the past decade. Implications. Taking into account the estimated reduction, the species’ biology and socioeconomic implications, wild rabbit in Portugal was listed in 2005 in the Near Threatened category under IUCN criteria. Because of its ecological and economic importance, this classification prompted the definition of several conservation actions aimed at the recovery of the species in Portugal.

Predictive niche modelling to identify potential areas of conflicts between human activities and expanding predator populations: a case study of game management and the grey mongoose, Herpestes ichneumon, in Spain

Context. The grey mongoose, Herpestes ichneumon L., is a protected species in Spain. Populations of grey mongoose are currently increasing in numbers, and potential conflicts with human interests involving predation of small-game species, may arise in the near future. Aims. We predicted potential suitable areas for the expansion of grey mongoose by using a niche modelling approach to detect areas of conflict with small-game hunting activities. Methods. We compared these areas with regions in which small-game hunting is an important economic activity. To produce a niche-suitability map we used Maxent and an internal (data-splitting) validation to assess the predictive performance of the model. Areas in which small-game hunting is important were identified by using a rabbit-abundance index. Key results. On the basis of suitability modelling, populations of grey mongoose will expand into southern and central Spain. The variables with higher predictive power are mainly climatic, although some mosaic habitat types are also important. Internal validation reveals a strong correspondence between predicted and observed records. The overlap of high-suitability areas with areas assigned with a high rabbit-abundance index indicated the existence of large regions of potential conflict with hunting interests. Conclusions. Predictions of niche modelling can be used to detect conflict areas between expanding species and human interests. As a consequence of the expansion of the grey mongoose, the incidence of non-selective predator control may increase, thereby posing a threat to other protected predators. Implications. Identified areas of likely conflict should be prioritised to delineate careful management programs in terms of people education, surveying, incentives and the detection of illegal predator-control activities.

The role of maternal antibodies in the emergence of severe disease as a result of fragmentation

Population fragmentation is a major problem for the conservation of mammalian species. Since the spread of an infectious disease is related to the intensity of contacts between individuals, fragmentation destabilizes the way the parasites circulate in their host population. Recently, Zinkernagel has proposed that a reduction in the frequency of infections by a parasite could lead to the emergence of severe forms of the disease, previously avoided because the disease was contracted early in life and attenuated by maternal antibodies. However, it is still unclear whether this change in disease expression increases the global mortality it induces because the disease becomes more severe and also less frequent. Here, we use a mathematical model to link population fragmentation with the hypothesis of Zinkernagel. Firstly, we show that there is a change in the severity of the disease during the fragmentation process, especially at a local scale, suggesting that host population fragmentation could be a widespread mechanism of disease emergence. Secondly, we show that the emergence of the severe form of the disease can lead to a significant increase in its induced mortality. Finally, we determine the types of interactions for which the fragmentation of the host population could be the most dangerous.